Means for producing alternating currents of low periodicity.



PATENTED DEC. 1, 1908.

W. MEISSNER.

- MEANS FOR PRODUCING ALTERNATING OURRENTS 0P LOW PERIODIGITY.

APPLICATION FILED APR. 1. 1903.

2 SHEBTS SHEBT 1.

N0 MODEL.

INVEIVTUR I wmvssss' PATENTED DEC. 1, 1903.

' W. MEISSNER. -MEANS FOR PRODUCING ALTERNATING GURRENTS OF LOWPERIODICITY.

APPLIOATION FILED APR. 1. 1903.

2 SHEETS-SHEET 2.

NO MODEL.

-', ATTD RNEY life. 74 5,508.

UNITED STATES Patented December 1, 1903.

PATENT @rnrcn.

MEANS FOR PRODUClNG ALTERNATiNG CURRENTS OF LOW PERlODiClTY.

SPECIFICATION forming part of Letters Patent No.

745,508, dated December 1, 1903.

Application filed April 1 1903. SerialNo.150,609. (No model.)

To all whom it may concern:

Be it known that I, WALDEMAR MEISSNER, engineer, a subject of the GermanEmperor, residing at 25 and 26 Joachimsthalerstrasse, Oharlottenbnrg,near Berlin, Germany, have invented certain new and useful Improvementsin Means for Producing Alternating Currents of Low Periodicity; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

My invention refers to means for generating alternating currents of verylow periodicity, such as are especially used in electromagneticreciprocating machines, and more especially in concussion rock-drills.

The invention consists in a continuous-current dynamo provided with aspecial commutator by means of which a pulsating current is generated inthe external circuit and of means for converting the pulsating currentthus obtained into an alternating current.

Of the accompanying drawings, Figure 1 is a diagram illustrating theprinciple upon which my invention is based. Fig. 2 is a diagrammaticalillustration of means for executing the invention; Fig. 3, adiagrammatical illustration of a specific embodiment of the invention,and 1 to 6 diagrammatical illustrations of various modification ofspecific means for carrying out the invention.

The same refei'ence'symbols apply to like parts in all the figures.

Referring at first to Fig. 1, c is meant to represent the commutator ofan ordinary continuous-current dynamo, and 61 (Z the fieldwindings ofthe same. The number of fieldwindings d in the divers figures indicatesthe number of poles the dynamo is meant to be provided with. c is aslip-ring supposed to be mounted on the armature-shaft of the dynamo andconductively connected to one of the barsfof the commutator c. 1, 2, and3 l are contact-brushes ofthe usual descriptiomof which twoviz., 1 and2-slide on the surface of the commutator c, and the third, 3, slides onthe surface of the ring 6, so that the latter is continuously inelectrical connection with the bar f. S is a polechanging deviceconsisting of three contact-pieces a b a, of which the first and lastare conductively connected with each other, and of two contact-arms tand 5,mounted on suitable pivots and mechanically coupled, so as to movein unison, as indicated in the drawings, but electrically insulated fromeach other. 3 is a translating device. The principle upon which mypresent invention is based will now be explained with reference to thisdiagram. \Vhen the commutator-barf registers with the brush 1, thepotential difference between brushes 1 and 3 will be zero. Then asbarfadvances toward brush 2, the potential difference will increase andwill reach a maximum value when f registers with brush 2. It will thenbegin to decrease and will again become zero whenf registers with 1, andthen the same play will be repeated. Thus a pulsating current will begenerated in the translating device 5, the periodicity of which for atwo-pole generator, as indicated in Fig. 1, will be equal to the numberof revolutions of the generator in this sense, that the current willpass from one maximum to the next in the same time in which thegenerator completes one revolution. Now if the pole-changing device 5 isoperated by any suitable mechanism, (not shown in the diagram,) whichmechanism is adapted to perform one reversal of the current every timesaid current becomes zero, this pulsating current will be converted intoan alternating current completing one full period in the same time inwhich the genera tor completes two full revolutions.

In Fig. 2 I have diagrammatically illustrat-ed specific means foraccomplishing the conversion of the pulsating current into analternating current. The generator is the same as in Fig. 1;pole-changing devices S and S It should be understood, however, thatthese two devices are not intended to be used simultaneously, but ratherrepresent different modifications of the electrical connections adaptedto bring about the desired result. The polechanging device consists of apair of sliprings 9 c and a pair of brushes 6 and 7, mounted to slide onthese contact-rings, respectively. Besides these slip-rings the deviceis provided with a third ring, consisting of two segments a and b,conductively connected to the slip-rings c and 6 respectively. areprovided,

Finally two brushes 1 and 5 but there are shown two sliding on theslip-ring Ct Z). In the case of S the translating device s is insertedbetween the brushes 4 and 5, and brush 7 is connected to brush 1 of thegenerator and brush 6 to brush 3 of the generator. In the caseillustrated with reference to S the translating device is insertedbetween the brushes 6 and 7, and brush 4 is connected to brush 1 of thegenerator and brush 5 to brush 3 of the generator. It will be evidentthat after every half-revolution of this pole-changing device has beencompletedthat is, every time the brushes 4 and 5 register with theinsulating portions of the circumference of the slip-ring whichseparates the segments a and b-a reversal of the current flowing in thecircuitof the translating device will be effected. Consequently-in orderto establish synchronism between the pole-changing devices S and S andthe generator, the revolution of the generator -shaft should betransmitted to the shaft of the pole-changing device by a gearing whichmakes the ratio of the two revolutions as two to one. It will be notedthat the devices S and S are in all respects equivalents of the deviceS. (Shown in Fig. 1.) It will also be noted that either way ofconnecting up these pole-changing devices with the generator and thetranslating device will have the same effect upon thelatter. When thereis no selfinduction in the translating device and the pole-changingdevice is mounted in such a way that the brushes 4 and 5 register withthe insulating-pieces separating the segments aand b at the same momentthat the barfin the commutator of the generator registers with the brush1, the current in the whole system will be naught during the reversal ofthe current; but when self-induction obtains in 8 there will beestablished a difference of phase between the current and theelectromotive force generated, and the consequence will be that at themoment of reversal a current of definite strength will be flowing in thecircuit, and this current would tend to create sparking at the brushesat and 5, with all the deleterious results following therefrom. In orderto obviate this difficulty, I make the brushes 4 and 5 so broad withrelation to the insulatingpieces in the circumference of thepole-changing device ct b that at the moment of reversal the segments aand b 'e short-circuited.

obtain between the two segments a and b, and the reversal will takeplace withou t sparking.

As I have hereinbefore speed of the shaft of the pole-changing devicewith reference to the speed of the generator-shaft should be as two isto one in this case; but this rule can be more generally expressed bystating that if the number of poles in the generator is 2 this ratioshould be as 13 is to two, and it will be seen that forp equal to two orfora four-pole generator this ratio is one. This means that thepole-changing device can be directly coupled with the said, the ratio ofshaft of the generator, or, in fact, be mounted upon it. A modificationof my present invention embodying this result is diagrammatically shownin Fig. 3. Instead of two fieldwindings d (1 four are provided,corresponding to the four poles of the dynamo; likewise, instead of onebrush 1 there are two. On the other hand, the two slip-rings e and e arereplaced by the single slip-ring 6 which is connected to the segment I),and the segment a is connected to the barf. The other connectionsstrictly correspond to the case shown in Fig. 2 with reference to S, andthe action of the whole arrangement will readily be understood with thehelp of the foregoing explanation.

From the foregoing, moreover, it will be understood that in order toobtain the desired synchronism between the generatorshaft and thepole-changing device it is only necessary that one reversal should takeplace every time the barfof the commutator c registers with one of thebrushes]. On the other hand, a reversal takes place everytime thebrushes 4 and 5 register with the insulating-pieces separating thesegments a and Z) on the circumference of the pole-changing device. Itfollows that it will be possible to vary the actual speed of thepole-changing device independently of the speed of the gen erator if thenumber of segments a and I) on the circnm ference of the pole-changingdevice is increased and corresponding segments are interconnected. Ifinstead of giving the ring of the pole-changing device two segments, itis formed of fonr,six,&c., segments,evidently a reversal does not takeplace after every half-revolution, but rather after every fourth, sixth,&c., part of a revolution, and in order to obtain synchronism thechanging device must be varied accordingly. If the number of pairs ofsegments ct and b be called 11 and the number of poles of the generator219 as above, the ratio obtaining between the speeds of the generatorand the pole-changing device would be 211: for synchronism, and thisvalue being dependent upon the value of n besides that of p it isevident that it can be made equal to 1 for any value of that isdivisible by 2 by giving n the value It is therefore possible to use adirect coupling between the generatorshaft and the pole-changing devicenot only in a four-pole machine, but likewise in an eight, twelve, the.pole machine.

In all cases the number of periods of the alternating current obtainedin the unit of time is half that of an alternating current that wouldbegenerated by the same machine when directly used as an alternator byproviding it with two slip-rings.

Referring now to Fig. et,it will be seen that it is in all generalfeaturesa repetition of the pole-changing device 8 in Fig. 2, the onlydifference being that instead of simple insulating-pieces being arrangedfor separating speed of the pole- IIO the segments a and b a number ofpieces are provided,which may be formed of insulating material, butwhich, however, I prefer to form of metal pieces separated from eachother by insulating material. With such insulating devices in order toshort-circuit the segments a and b at the moment of reversal the brushes4: and 5 are made in pairs, the single members of each pair being placedat circumferential distances corresponding to the circumferential lengthof the insulating device separating the conductive segments. Thisarrangement I have found advantageous in all cases in which the tensionof the current to be generated is not quite small. Practical experiencehas shown that with ordinary insulating-segments, as indicated in theforegoing figures, the apparatus acts satisfactorily for a short time;but soon a film of metal forms on the surface of the insulatingsegmentsand violent sparking is the consequence. On the other hand, by applyingthe insulating device, consisting of metal pieces separated by pieces ofinsulating material, this difficulty is absolutely avoided. I find,moreover, that it is not so important to increase the circumferentiallength of the insulated pieces as it is to increase the number of themin order to obviate sparking. It will be readily seen thatthe effect ofthis arrangement is exactly the same as the effect of that describedwith reference to the foregoing figures, if only the condition befulfilled that the conductive segments are not shorter than the distanceof the members of each pair of brushes 4 and 5. It is therefore possibleto increase the total length of the insulated segments up to one-quarterof the total circumference for each insulating device, and by thisdisposition the maximum of security against sparking is obtained.

Fig. 5 shows another pole-changing device.

modification of the It is evident from the foregoing that in order toobtain the desired reversal with the described arrangements the brushesor pairs of brushes and 5- must be placed exactly opposite each other;but if instead of using one two-pole-changing device I use twoone-pole-changing devices I will evidently be free to place the brushesat any part of the circumference if the segments of the slip-rings arearranged accordingly. Thus, for instance, the brushes may be placed inimmediate vicinity of each other, as in Fig. 5, and in some cases Iprefer this arrangement, because when sparking occurs in consequence ofa faulty adjustment of the brushes they can be controlled more easilywhen both are located at the same side of the pole-chang ing device.

The above-described arrangement can with proper modifications also beemployed for producing polyphase alternating currents instead ofsingle-phase currents, and the simplest case is obtained in theproduction of two currents removed by one-quarter of a period from eachother. Such currents can CD U be produced from the generator, as abovedescribed, by providing it with two slip-rings e, each of which isconnected to a bar of the commutator a, such bars being chosen as areremoved by one hundred and eighty degrees from each other. I prefer,however, to use the arrangement illustrated in Fig. 6,in which only oneslip-ring e is provided, and the two currents are taken from brushes 1and 3 and 2 and 3, respectively. The corresponding pole-changing deviceis shown in proper connection with this arrangement in Fig. 6.

Fig. 7 shows this modification applied to the case of a four-polemachine, as in Fig. 3. Both figures will be readily understood withoutbeing explained in detail. It will sufficc to say that in both cases thereversal of the current issuing from the negative pole of the generatortakes place at the moment illustrated in the figure, and afterone-quarter of a revolution of the pole-changing device the othercurrent removed by one-quarter of a period will be reversed. In thefigure two translating devices .9 and s are shown corresponding to thetwo currents, and the difference of phase in both is indicated by theirrelative angular position.

As will be seen by persons conversant with the art the same method canbe employed for obtaining three or more polyphase currents; but it willbe observed that by adjusting the brushes 1 2, 850., at angulardistances of one hundred and twenty degrees from each other a differenceof phase of only sixty de grees is obtained, so that it will benecessary to arrange the connections accordingly. In all cases it willbe necessary to employ separate pole-changing devices for each current;but it is evident that these devices may be mounted on the same shaft.

The generator maybe driven either mechanically or electrically, and forthis latter purpose the mains m and m are shown on all the drawings.Moreover, in all the figures I have shown the field of the generator ina shunt connection; but series windings might also be employed, ifdesirable, either by using the continuous current of one of the mains mor m or also the pulsatory current generated by the dynamo itself. Iftwo polyphase currents be generated, as in the cases of Figs. 6 and 7,both currents should be superposed for feeding a field-winding connectedin series. Assuming the curve shapes of the currents to be true sines,the sum of both currents would in this case be a true continuouscurrent.

Returning now to Fig.2 and assuming that the translating device 5contains an appreciable amount of self-induction an appreciabledifference of phase between the current generated and the terminalelectromotive force of the generator will be established. Consequently,since reversal is effected at the moment in which the terminalelectromotive force of the generator becomes naught, acurrent ofdefinite intensity will still be flowing in the circuit. It is to beremarked that at the moment of reversal, which is shown in the drawings,the brushes 4 and are not only short-circuited by the segments a and b,but 5 also by the circuit formed by the brushes 1 and 3 and theslip-ring e and bar f. The long arrows disposed along the differentbranches of the circuit are meant to represent the direction of thecurrent flowing in that to branch at the moment before the brushes 4 and5 are short-circuited-thatis,when brush 4 touches segment a only andbrush 5 touches segment I) only. The short arrows indicate the directionof the current in the respective parts of the circuit at the momentimmediately following the commutation. It is to be noted that inconsequence of the difference of phase between the current and theelectromotive force a reversion of the current only takes place in thatpart of the circuit which is represented by the brushes 1 and 3,slip-ring e, and barf. At the moment of commutation the part of thecurrent flowing in the segments 3 and b will be transferred to thisbranch, and there will be no sparking, provided this branch be free fromself-ind'uction. It is evident that this condition can be practicallyfulfilled in allcases, and consequently sparking can be effectuallyavoided, though the translating device .9 may contain any amount ofself-induction.

Having now particularly described and ascertained thenature of my saidinvention and in what manner the same is to be performed,

I declare that what I claim is rents of low periodicity which meansconsist 1. Means for producing alternating curin the combination, with acontinuous-currents of low periodicity of any number of rent dynamo, ofa slip-ring formed of a pluphases which means consist in thecombinarality of pairs of segments, means for elec- 105 tion, with acontinuous-current dynamo, of a trically connecting said pairs ofsegments al- 0 pole-changing device inserted between the ternately to abar of the commutator and to brushes and one bar of the commutator ofthe brushes of the said dynamo, and means said dynamo and means foroperating the forrotatingsaid slip-ringin synchronism with said polechanging device in synchronism the commut-atorof said dynamo,substantially 1 10 with the commutator of said dynamo, subas and for thepurpose described.

stantially as and for the purpose described. 7. Means for producingalternating cur- 2. Means for producing alternating currents of lowperiodicity which means consist rents of low periodicity which meansconsist in the combination, with a continuous-curin the combination,with a continuous-current dynamo havingp pairs of poles, of aslip- 115rent dynamo, of a slip-ring mounted on the ring formed of 2n segments inelectrical comarmature-shaft and connected to one of the munication withone commutator-bar and bars of the commutator of said dynamo, a withthebrushesofsaid dynamo,respectively, brush mounted to slide on saidslip-ring, a and means for rotating said slip-ring with a circuit formedbetween said brush and a speed of 211 :p multiplied by the speed of said120 brush of the dynamo, a pole-changing device commutator of saiddynamo, substantially as inserted in said circuit, and means for operandfor the purpose described.

ating said pole-changing device in synchro- 8. Means for producingalternating curnism with the armature of said dynamo, subrents of lowperiodicity which means consist stantially as and for the purposedescribed. in the combination, \'ith a continuous-cur- 12 3. Means forproducing alternating current dynamo having}; pairs of poles, of a slip-6o rents of low periodicity which means consist ring formed of pairs ofsegments alternately in the combination, with a continuous-curconnectedelectrically to the brushes and one rent dynamo, of a slip-ring dividedinto segcommutator-barof said dynamo, respectively, ments, such segmentsbeing in electrical comthe number of said pairs of segments being 130munication with the brushes and with one equal top 2and saidslip-ringbeingmounted 6= barof the commutator of the dynamo, respecuponand adapted to rotate with the commudynamo, substantially as and for thepurpose set forth.

4. Means for producing alternating cur- 7o rents of low periodicitywhich means consist in the combination, with a continuous-currentdynamo, of a slip-ring consisting of segments, such segments being inelectrical communication with the brushes and with one of thecommutator-bars, respectively, of the said dynamo, the segments of theslip-ring being separated fronr each other by a plurality of insulatedpieces, and means for rotating the said slip-ring in synchronism withthe said dynamo, substantially as and for the purpose described.

5. Means for producing alternating currents of low periodicity whichmeans consist in the combination, with a continuous-current dynamo, of aslip-ring formed of segments, such segments being in electricalcommunication with the brushes and with one commutator-bar,respectively, of the said dynamo and being separated from each other by9 a insulating devices, each device comprising a plurality of insulatedpieces, of pairs of brushes codperating with said slip-ring the membersof each pair being removed from each other by the angular length of eachin- 5 sulating device and being conductively connected with each other,and means for rotating said slip-ring in synchronism with the commutatorof the said dynamo, substantially as and for the purpose set forth. I00

6. Means for producing alternating curtively, and means for rotating theslip-ring tator-shaft of said dynamo, substantially as in synchronismwith the commutator of the and for the purpose set forth.

9. Means for producing polyphase aiternatthe commutator of said dynamo,substantially 1'0 ing currents of 10W periodicity which means as and forthe purpose described. consist in the combination, with a continuous- Intestimony whereof I have affixed my sigcurren'o dynamo, of a slip-ringfor each curnature in presence of two Witnesses.

5 rent of separate phase, such slip-rings con- T sisting of segmentsaiternatelyconnected eiec- VVALDEMAR MEISSL tricaily to respectivebrushes and to a com- Witnesses: munator-bar of said dynamo, and meansfor HENRY HASPER,

rotating, said slip-rings in synchronism with VOLDEMAR HAUPT.

